The secondary critical speed of a shaft occurs at
A)Twice the primary critical speed
B)Occurs only when there are more than 2 rotors on a shaft
C)Four times the primary critical speed
D)If the externam exciting system has a frequency other than the primary critical speed
E)Half the primary critical speed

Question

Quizplus · Accepted Answer

The secondary critical speed of a shaft occurs at twice the primary critical speed. This is because the critical speeds of a rotating shaft are proportional to the square root of the stiffness to mass ratio, and as the mode shapes of vibration become more complex, the critical speeds increase, typically in a sequence where the secondary is roughly twice the primary, though exact relationships can depend on the specific system configuration.

The Secondary Critical Speed of a Shaft Occurs at